Generally, the process of electrostatographic production is initiated by exposing light representing an original document onto a substantially uniformly charged photoreceptive member, resulting in the creation of a latent electrostatic image of the original document on the photoreceptive member. This latent image is subsequently developed into a visible image by a process in which developer material is deposited onto the surface of the photoreceptive member. Typically, this developer material comprises carrier granules having toner particles adhering triboelectrically thereto, wherein the toner particles are electrostatically attracted from the carrier granules to the latent image for forming a developed powder image on the photoreceptive member. Alternatively, liquid developing materials comprising a liquid carrier having toner particles immersed therein have been successfully utilized to develop electrostatic latent images, wherein the liquid developing material is applied to the photoconductive surface with the toner particles being attracted toward the image areas of the latent image to form a developed liquid image on the photoreceptive member. Thereafter, the image may be permanently affixed to the copy substrate for providing a "hard copy" reproduction or print of the original document or file. In a final step, the photoreceptive member is cleaned to remove any charge and/or residual developing material from the photoconductive surface in preparation for subsequent imaging cycles.
The described electrostatographic production process is well known and is useful for light lens copying from an original document. Analogous processes also exist in other electrostatographic production applications such as, for example, digital laser printing where a latent image is formed on the photoconductive surface by a modulated laser beam, or ionographic printing and reproduction where charge is deposited on a charge retentive surface in response to electronically generated or stored images.
In a liquid development system, an intermediate belt transfers the toner particles of the developed image from the photoreceptive member to the copy substrate. The transfer belt first passes under a heating element to melt the toner particles before they bond to the copy substrate. During the heating process, the toner particles maintain their position on the transfer belt, so as not to alter the image they represent while softening and coalescing. The transfer belt thereafter advances to a fusing station where a pressure roll bonds the melted toner to the copy substrate before it exits the printing machine. After the copy substrate leaves the machine, the belt continues to advance towards the photoconductive member to transfer the next image. Before the transfer belt contacts the photoconductive member, the belt's surface is cooled to prevent damage to the photoconductive member by the residual heat that otherwise remains on the belt.
One conventional method of removing heat from the surface of the transfer belt involves the use of an active cooling system. A typical vapor cycle cooling system exacts heat from the belt using the principles of evaporation and condensation. On passing a liquid from its liquid state to a vaporous state, the liquid absorbs the heat and subsequently gives it off again on condensing. A compressor draws away the vapor, compresses it, passes it to a condenser, where it parts with its heat. Another method of removing heat from the transfer belt involves the use of a non-vapor cycle system. In the non-vapor cycle system large amounts of air circulate through the printing machine to cool the belt before an exhaust expels the air from the machine and the room it occupies. Alternatively, the circulation of water overcomes problems with duct work, noise and dust control which are associated with the movement of air.
While both the vapor and non-vapor systems maintain control over one temperature exchange on the transfer belt surface; however, it is desirable to have a system that maintains control over two temperature exchanges. This is especially important in electrostatographic printing machines inasmuch as a single heat recovery management system can heat the transfer belt and then cool it. Such a system conserves energy and provides substantial operating cost reduction.
The following disclosures may relate to various aspects of the present invention.